The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Handheld tools are often pneumatically operated, such as the tool illustrated and described in EP 1028826 B1. The pneumatically operated linear oscillating drive of such a handheld tool has a motor housing and a piston arranged in the motor housing, which separates two working chambers of the motor housing from one another and has a piston skirt facing towards one of the two working chambers. A supply of compressed air to the two working chambers is controlled via a compressed air supply line to the motor housing and a slide valve. The compressed air is supplied in such a manner that the piston is alternatively driven in one and the other direction and thus carries out an oscillating back and forth motion. The two working chambers are vented via an exhaust air opening in the motor housing.
The piston drives an oscillating tool, such as a saw blade or a filing tool, by means of a piston rod. According to EP 1028826 B1, the piston base is thin-walled and arched and transitions at its periphery into a thin-walled cylindrical sleeve in order to keep small the mass of the piston, and thus also the amount of reaction forces to be dissipated during its oscillating movement, small. Such a thin-walled sleeve is also referred to in the application as a piston skirt. The piston base and the cylindrical sleeve forming the piston skirt form a piston crown, whose interior faces away from one of the two working chambers. In other words: a section through the piston in the movement direction yields a U-shaped cross section with the two legs of the U pointing towards one of the working chambers.
The energy stored in the compressed air is ultimately converted by such a handheld tool into mechanical work. In order to be able to generate forces as large as possible for specific dimensions and specific pressures and to be able to convert most of the energy connected with producing compressed air into mechanical energy, it is of general interest to ensure a good efficiency of the pneumatic linear oscillating drives. Under constant pneumatic conditions such as pressure and flow rate, for example, the cutting power of a saw connected to the linear oscillating drive increases with improved efficiency.